The heart of a computer is a magnetic disk drive which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
There are many different types of read and/or write magnetic heads used in magnetic disk systems. One such type of read/write head is a tunneling magnetoresistive (TMR) head. One drawback with using a typical TMR head is that there is a weak antiferromagnetic (AFM) coupling between the reference layer and keeper layer through the antiferromagnetic (AFM) coupling layer, where this AFM coupling is referred to as AFM coupling field HeP2. Previous attempts to increase HeP2 have resulted in undesirable side effects. For example, an increase in the AFM coupling between the reference layer and the keeper layer can cause an increase in the ferromagnetic coupling between the reference layer and the free layer which degrades the performance of the TMR head. In another example, tunneling magnetoresistance can decrease when the AFM coupling between the reference layer and the keeper layer increases.
Therefore, it would be beneficial to have a TMR head with increased AFM coupling between the reference layer and the keeper layer without substantially increasing the ferromagnetic coupling between the reference layer and the free layer and without substantially decreasing the tunneling magnetoresistance of the head.